Evaporation is a significant contributor to water loss, and a major contributor to maintenance costs, in residential and commercial swimming pools and spas. For example, the evaporative loss from an unoccupied 10,000 sq ft pool with a water temperature of 80° F., an air temperature of 78° F., and relative humidity of 50 percent is about 132 liters/hour or nearly 35 gallons/hour. See M. M. Shah, HPAC Engineering, Oct. 1, 2011. Over a 12 hour period at these conditions water loss can exceed 400 gallons. This volume can nearly double if the pool is fully occupied. It is, therefore, desirable to reduce or eliminate evaporation, especially in drought stricken areas such as the southwestern United States where water resources are limited.
Traditional pool covers consist of a physical barrier that is fitted over the pool surface when the pool is not in use. A properly fitted cover can reduce evaporative water loss up to 97% (See World Wide Web at daisypoolcovers.com.au/daisy-saves/evaporation/). However, physical covers are only effective when the pool or spa is not in use.
Recently, so called “liquid” covers have become available. These products spread a thin layer of surface active material over the surface of the pool creating a monomolecular film that suppresses water and heat loss. “Liquid” covers can provide some benefit even when the pool or spa is in use since the film is fluid and reforms after disruption by swimmers. The film-forming materials used in these products range from surface active polymers, such as modified polysiloxanes (Aquatain™) to simple fatty alcohols (waterSavr™).
A number of surface active materials are commonly introduced to pools and spas during use. Sunscreens and suntan lotions contain several different surface active ingredients including emollients such as isopropyl isostearate, caprylic/capric triglyceride, C12-C15 alkyl benzoate, and diisopropyl sebacate. Additionally, wax esters, cholesterol esters, and free fatty acids are present from human sebum. This collection of oily, greasy materials (typically referred to as FOG for Fats, Oils, Grease) represents a significant soil load, causing pool water to grow cloudy over time and forming a scum ring around the edge of the pool.
There is an opportunity to use these FOG materials as precursors to liquid films to aid in reducing water evaporation and retaining heat while simultaneously clarifying the water, reducing filter head pressure and pump run times by breaking the FOG components down into constituent fatty acids and fatty alcohols.